Predation of Overwintering Larvae of Codling Moth (Cydia pomonella (L.)) by Birds

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Abstract
At Long Ashton, near Bristol [England], observations in an unsprayed cider-apple orchard suggested high mortality of codling moth larvae overwintering under the bark, by bird predation. In experiments in cider-apple orchards in 3 winters (early 1971, 1972 and 1973), larvae were allowed to spin cocoons under the bark of apple logs which were then tied into trees. Some logs were caged in wire netting to exclude birds. On the caged logs there were few or no losses of larvae through winter and spring. On the exposed logs the pooled losses over the same period were 94.7%, 94.9% and 95.6% in the 3 winters. In the latter 2 experiments, the initial number of larvae on individual logs varied from 1-30. Most larvae were taken in the 1st few weeks; the percentage loss was higher for 30, 20 or 14 larvae than for 7 or less. The early density of wild larvae on the trees was equivalent to about 5 or 6/log. The only bark-hunting birds seen frequently in the orchards were blue tits and (fewer) great tits (Parus caeruleus L. and P. major L.). They were seen working the bark and left identifiable marks and holes there and the remains of cocoons. Birds are a potent factor in the control of codling moth populations, at least in orchards of the type studied.